A vest that administers an electric shock has been designed to help heart patients in the United States.

The electric vest is shaped like a bra and is set off if the wearer's heart stops beating. As many as one in four patients in the US awaiting a heart transplant die when their heart stops beating and starts to quiver uncontrollably.

Without an electric shock to re-start it, death is almost inevitable.

Positive results

Initial tests on the vest have been positive and it is about to be tried out on a group of volunteers from Philadelphia.

Vest developed at Temple University

"There have been two patients who have had ventricular fibrillation," said Howard Eisen, head of the transplant research unit at Temple University in Philadelphia.

"In both circumstances the vest has successfully detected the rhythm and shocked them back to a normal rhythm. So essentially the vest has saved their lives."

The vest has a series of electrodes, strapped to the wearer's chest to listen for these fibrillating rhythms. If one of these rhythms is detected, the vest automatically squirts a gel that conducts electricity onto the patient's body.

At the same time, it sounds an audible alarm so the patient can prepare for what follows - five electric shocks, one every thirty seconds.

The vest also carries a sound transmitter, which warns people nearby not to touch the patient in case they too get an electric shock.

'Cheaper than surgery'

There are already devices that can be implanted inside the body to give an electric shock from within. But they have to be removed by surgery once the patient gets a heart transplant.

Dr Eisen said that for these patients an electric vest would be an ideal alternative.

"The purpose of this device is in people who will not always be at risk of ventricular fibrillation, that you can use this device just during the time they're at risk," he said.

"So in other words someone who is waiting for a transplant. Once they get transplanted, their new heart is not at risk of developing these rhythms, so then they don't have to wear the vest."

"The vest is extremely inexpensive compared to surgery and can be used over and over again," he said.

Although the electric vests are undoubtedly unusual, the idea could eventually save hundreds of lives.